The application of an optical navigation system for use in a computer mouse for navigating a cursor has become almost universal. Optical navigation system tracks the movement of the optical navigation system relative to the target surfaces such as a mouse pad or a work surface. A typical optical navigation system uses a light source and an image sensor to successively capture frames of image data of the target surface. The optical navigation system compares the successive image frames and determines the relative movements between the optical navigation system and the target surface based on these image frames. The navigation system subsequently processes and further translates the movement data to a cursor movement on the computer.
With an input device such as an optical mouse which is manually manipulated, there is a need to recognize when the mouse has been lifted off the navigation surface, during repositioning or when the mouse is moved away from the edge of the navigating surface. It is important to have the navigation operation to be temporarily suspended during lifting without moving the cursor. Therefore, in order for the input device to perform properly, it is crucial to detect the lift from the target surface beyond a certain height and be able prevent a mouse from tracking to avoid cursor skating.
There are conventional lift detection techniques that can be implemented on a navigation system in order to prevent the mouse from tracking that may be based on image defocus or image surface quality value. However, these lift detection techniques typically involve complex steps and are usually integrated as part the system during the chip design.